1. Field of the Invention
The present invention relates to a circuit breaker, and more particularly to a temperature sensitive circuit breaker that opens the circuit when a high temperature condition or a current overload exists.
2. Description of Related Art
With reference to FIG. 6, a conventional circuit breaker in accordance with the prior art comprises a base (50), a core (53), two U-shaped rails (54), two prongs (55), a connector (60), a first spring (64) and a second spring (65). A cavity (51) centrally defined in the base (50) and extending to the top of the base (50). A chamber (52) is defined in the base (50) and communicates with the cavity (51). The core (53) is secured in the cavity (51) and made of meltable material so that the core (53) will melt and the melted material will flow into the chamber (52) due to a high temperature caused by a current overload. The U-shaped rails (54) are attached perpendicularly to the top of the base (50) on diametrically opposite sides of the cavity (51). Each rail (54) has a slot (not shown) defined in the bottom of the rail (54) aligning with and facing the slot in the other rail (54). The prongs (55) extend through the base (50), and part of each prong (55) is embedded in tile base (50). A convex contact (551) is formed on a first end of each prong (55) and aligns with the slot in the rail (54). A second end of each prong (55) is electrically connected to the circuit.
The connector (60) is electrically connected between the two prongs (55) and comprises two slides (61), a bridge (62) and a rod (63). The slides (61) are respectively slidably mounted in the U-shaped rails (54). Each slide (61) has a first side (not numbered) abutting the contract (551) on the prong (55) and a second side (not numbered) electrically connected to a bridge (62) so that the two prongs (55) are electrically connected to each other. The rod (63) has a first end attached to the bottom of the bridge (62) and a second end securely inserted into the core (53). The first spring (64) mounted around the rod (63) and is compressed between the top of the base (50) and the bottom of the bridge (62). A second spring (65) has first end attached to the top of the bridge (62) and a second end attached to the casing (70) so the second spring (65) is stretched between the bridge (62) and the casing (70).
With reference to FIG. 7, when the circuit (not shown) to which the breaker is attached has a current overload and a resultant high temperature, the core (53) melts and flows into the chamber (52). This frees the rod (53) from the core (53), and restitution force in the first and second springs (64, 65) detach the bridge (62) from the rail (54). Then the circuit to which the breaker is attached is broken because the two prongs (55) are disconnected from each other.
The conventional circuit breaker breaks the circuit only when the circuit has a high temperature that is caused by an overload current. However, a current overload does not necessarily cause a high temperature so that the current overload may damage the circuit. Furthermore, the conventional circuit breaker comprises many small elements, such as the rod (63) and the two springs (64, 65) that are hard to assemble in the casing (70), and conventional circuit breaker can only be used one time because the core (53) can not be restored to its original configuration after being melted.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional circuit breaker.
The main objective of the present invention is to provide a simpler circuit breaker that opens the circuit to which it is attached whatever a high temperature or a current overload in the circuit.
To achieve tile objective, the circuit breaker in accordance with the present invention comprises two contacts electrically mounted on a circuit board and an insulating pivot seat attached to the circuit board between the two contacts. A lever has a first end pivotally connected to the pivot seat and connected to one of the contact and a second end electrically connected to the other contact. A non-metallic expansive rod is mounted on the circuit board below the lever to push the lever upwardly to make the second end of lever disconnect from the contact when a high temperature in the circuit is transferred to the expansive rod. A breaking member is connected between a second end of the lever and the other contact on the circuit board. A high temperature associated with a current overload causes the breaking member to melt and open a circuit to which the breaker is attached.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.